/****************************************************************************
 *
 * Copyright 2016 Samsung Electronics All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
 * either express or implied. See the License for the specific
 * language governing permissions and limitations under the License.
 *
 ****************************************************************************/
/****************************************************************************
 * fs/dirent/fs_readdir.c
 *
 *   Copyright (C) 2007-2009, 2011 Gregory Nutt. All rights reserved.
 *   Author: Gregory Nutt <gnutt@nuttx.org>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name NuttX nor the names of its contributors may be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <tinyara/config.h>

#include <string.h>
#include <dirent.h>
#include <errno.h>

#include <tinyara/fs/fs.h>
#include <tinyara/fs/dirent.h>

#include "inode/inode.h"

/****************************************************************************
 * Private Functions
 ****************************************************************************/

/****************************************************************************
 * Name: readpseudodir
 ****************************************************************************/

static inline int readpseudodir(struct fs_dirent_s *idir)
{
	FAR struct inode *prev;

	/* Check if we are at the end of the list */

	if (!idir->u.pseudo.fd_next) {
		/* End of file and error conditions are not distinguishable
		 * with readdir.  Here we return -ENOENT to signal the end
		 * of the directory.
		 */

		return -ENOENT;
	}

	/* Copy the inode name into the dirent structure */

	strncpy(idir->fd_dir.d_name, idir->u.pseudo.fd_next->i_name, NAME_MAX + 1);

	/* If the node has file operations, we will say that it is
	 * a file.
	 */

	idir->fd_dir.d_type = 0;
	if (idir->u.pseudo.fd_next->u.i_ops) {
#ifndef CONFIG_DISABLE_MOUNTPOINT
		if (INODE_IS_BLOCK(idir->u.pseudo.fd_next)) {
			idir->fd_dir.d_type |= DTYPE_BLK;
		}
		if (INODE_IS_MOUNTPT(idir->u.pseudo.fd_next)) {
			idir->fd_dir.d_type |= DTYPE_DIRECTORY;
		} else
#endif
		{
			idir->fd_dir.d_type |= DTYPE_CHR;
		}
	}

	/* If the node has child node(s) or no operations, then we will say that
	 * it is a directory rather than a special file.  NOTE: that the node can
	 * be both!
	 */

	if (idir->u.pseudo.fd_next->i_child || !idir->u.pseudo.fd_next->u.i_ops) {
		idir->fd_dir.d_type |= DTYPE_DIRECTORY;
	}

	/* Now get the inode to vist next time that readdir() is called */

	inode_semtake();

	prev = idir->u.pseudo.fd_next;
	idir->u.pseudo.fd_next = prev->i_peer;	/* The next node to visit */

	if (idir->u.pseudo.fd_next) {
		/* Increment the reference count on this next node */

		idir->u.pseudo.fd_next->i_crefs++;
	}

	inode_semgive();

	if (prev) {
		inode_release(prev);
	}

	return OK;
}

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Name: readdir
 *
 * Description:
 *   The readdir() function returns a pointer to a dirent structure
 *   representing the next directory entry in the directory stream pointed
 *   to by dir.  It returns NULL on reaching the end-of-file or if an error
 *   occurred.
 *
 * Inputs:
 *   dirp -- An instance of type DIR created by a previous call to opendir();
 *
 * Return:
 *   The readdir() function returns a pointer to a dirent structure, or NULL
 *   if an error occurs or end-of-file is reached.  On error, errno is set
 *   appropriately.
 *
 *   EBADF   - Invalid directory stream descriptor dir
 *
 ****************************************************************************/

FAR struct dirent *readdir(DIR *dirp)
{
	FAR struct fs_dirent_s *idir = (struct fs_dirent_s *)dirp;
	struct inode *inode;
	int ret;

	/* Verify that we were provided with a valid directory structure */

	if (!idir) {
		ret = EBADF;
		goto errout;
	}

	/* A special case is when we enumerate an "empty", unused inode.  That is
	 * an inode in the pseudo-filesystem that has no operations and no children.
	 * This is a "dangling" directory entry that has lost its children.
	 */

	inode = idir->fd_root;
	if (!inode) {
		/* End of file and error conditions are not distinguishable
		 * with readdir.  We return NULL to signal either case.
		 */

		ret = OK;
		goto errout;
	}

	/* The way we handle the readdir depends on the type of inode
	 * that we are dealing with.
	 */

#ifndef CONFIG_DISABLE_MOUNTPOINT
	if (INODE_IS_MOUNTPT(inode) && !DIRENT_ISPSEUDONODE(idir->fd_flags)) {
		/* The node is a file system mointpoint. Verify that the mountpoint
		 * supports the readdir() method
		 */

		if (!inode->u.i_mops || !inode->u.i_mops->readdir) {
			ret = EACCES;
			goto errout;
		}

		/* Perform the readdir() operation */

		ret = inode->u.i_mops->readdir(inode, idir);
	} else
#endif
	{
		/* The node is part of the root pseudo file system */

		ret = readpseudodir(idir);
	}

	/* ret < 0 is an error.  Special case: ret = -ENOENT is end of file */

	if (ret < 0) {
		if (ret == -ENOENT) {
			ret = OK;
		} else {
			ret = -ret;
		}

		goto errout;
	}

	/* Success */

	idir->fd_position++;
	return &idir->fd_dir;

errout:
	set_errno(ret);
	return NULL;
}
